Skeletal Muscle Ryanodine Receptor Permeation and Self Counter-Ion Flow

骨骼肌 Ryanodine 受体渗透和自反离子流

• 批准号: 7920082
• 负责人: Michael Fill
• 金额: $ 30.87万
• 依托单位: RUSH UNIVERSITY MEDICAL CENTER
• 依托单位国家: 美国
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-09-01 至 2013-02-28
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7920082
• 关键词: Amino Acid Motifs; Amino Acids; Attenuated; Biological Assay; Cations; Cells; Central Core Myopathy; Characteristics; Charge; Data; Detection; Dimensions; Disadvantaged; Disease; Event; Image; Ions; Knowledge; Lipid Bilayers; Location; Mediating; Membrane Potentials; Modeling; Molecular; Muscle; Mutation; Physiological; Potassium Channel; Process; Publishing; RyR1; Ryanodine Receptor Calcium Release Channel; Ryanodine Receptors; Sarcoplasmic Reticulum; Signal Transduction; Site; Skeletal Muscle; Structure; Testing; Time; Vesicle; Work; attenuation; base; cell type; computerized data processing; driving force; mutant; novel; theories

DESCRIPTION (provided by applicant): Depolarization of skeletal muscle initiates Ca release through type-1 ryanodine receptor (RyR1) Ca release channels in the sarcoplasmic reticulum (SR). Concerted opening of multiple RyR1 channels at discrete SR Ca release sites generates small localized release events called Ca sparks, the elemental unit of SR Ca release in cells. Spark recruitment/summation is what generates the global Ca release transient that drives muscle contractility. Many studies have focused on the onset and termination of the Ca release transient. Fewer have focused on the RyR conduction/selectivity and none (to our knowledge) have studied what physiological ramifications the RyR permeation characteristics of RyR1 have on cellular Ca signaling phenomena like the Ca release transient. The RyR pore is thought to have a structure analogous to that of the bacterial K channel (KcsA). The RyR has a lumenal loop which contains a predicted pore helix and an amino acid motif (GGGIG) identified as a selectivity filter. Unlike the KcsA pore, the RyR pore has high conductance and is poorly selective. Published works as well as our own preliminary data have revealed some key molecular determinants that define the characteristic high conductance, poor selectivity of the RyR1 pore. This includes some naturally occurring mutants associated with central core disease (CCD). This proposal combines this information to define the mechanisms that govern RyR1 permeation under physiological conditions and applies this knowledge to define some key physiological ramifications of the single channel RyR1 permeation process. The following hypothesis is tested. Hypothesis: In cells, the poor selectivity of the RyR1 channel allows multiple ions (Ca, Mg & K) to compete for occupancy of the open pore. While this competition attenuates the net SR Ca efflux through the open pore, it also allows the pore to mediate its own counter ion flux during the Ca release process. This self counter-ion flow effectively clamps local SR membrane potential far from the Ca Nernst potential (ECa) making the trans-SR Ca driving force primarily dependent on the trans-SR Ca concentration gradient. This is physiologically important because it allows the RyR channel to sustain Ca release over an extended period of time (>5 ms or the rise time of Ca transient). The specific aims are: (1) Define how known molecular determinants of RyR1 permeation combine to generate/influence the conductance and selectivity of the open RyR1 pore. (2) Define functional consequences of the relatively poor selectivity of the RyR1 pore; namely attenuation of net SR Ca efflux through the open pore and the capacity of the open pore to carry its own counter ion flux during SR Ca efflux.

描述（由申请人提供）：骨骼肌的去极化通过1型ryanodine受体（RYR1）Ca释放通道的释放释放。在离散的SR CA释放位点上的多个RYR1通道的一致开放产生了称为CA Sparks的小型局部释放事件，这是SR CA的元素单位释放的细胞中的元素。 Spark招募/总和是生成驱动肌肉收缩力的全球CA释放瞬变。许多研究集中在CA释放瞬态的发作和终止上。更少的专注于RYR的传导/选择性，而没有（据我们所知）研究了RYR1在CA释放瞬变（例如CA释放瞬变）上具有RYR渗透特征的生理后果。 RYR孔被认为具有类似于细菌K通道（KCSA）的结构。 RYR具有一个灯笼环，其中包含一个预测的孔螺旋和一个被识别为选择性滤波器的氨基酸基序（GGGIG）。与KCSA孔不同，RYR孔的电导率很高，选择性较差。发表的作品以及我们自己的初步数据揭示了一些关键的分子决定因素，这些决定因素定义了特征性高电导率，RYR1孔的选择性差。这包括一些与中心核心疾病（CC​​D）相关的天然突变体。该提案结合了这些信息，以定义在生理条件下控制RYR1渗透的机制，并应用此知识来定义单个通道RYR1渗透过程的某些关键生理后果。测试了以下假设。假设：在细胞中，RYR1通道的选择性差允许多个离子（CA，MG＆K）竞争开放孔的占用。尽管该竞争通过开放孔削弱了净SR CA流出，但它还允许孔在CA释放过程中介导其自己的反离子通量。这种自动离子流有效地夹住了局部SR膜电位，远离CA Nernst电位（ECA），使Trans-SR CA驱动力主要取决于反式SR CA浓度梯度。这在生理上很重要，因为它允许RYR通道在很长的时间内维持CA释放（> 5 ms或CA瞬态的上升时间）。具体目的是：（1）定义RYR1渗透的已知分子决定因素如何结合起来产生/影响开放式RYR1孔的电导和选择性。 （2）定义了RYR1孔的选择性相对较差的功能后果；即，通过开放孔和开放孔在SR CA流出期间携带自己的反离子通量的能力来衰减净SR CA外排。